The use of molding materials having a relatively high specific gravity is known. Such molding materials contain a polymeric resin and a high density filler such as iron oxide. However, in such molding materials the amount of iron oxide which can be included is limited as the thermal conductivity properties of the molding material are relatively poor. Lower thermal conductivity leads to relatively longer cycle times to allow the molding material to cool after molding. In comparison, the molding materials having metal based fillers with a higher thermal conductivity leads to relatively smaller process windows because the material has poor flow characteristics and cools relatively fast.
Many heavy polymeric materials are filled with high heat conductive additives such as metal powder or fibers. The addition of these materials leads to tight process windows in molding because of the immediate freezing when the molten material contacts the cold wall of the tool. This fast freezing leads to high injection speed and low flow length to wall thickness ratio at the produced part.
It is an object of the present invention to provide a molding material having a high specific gravity and optimally controlled thermal conductivity properties to reduce or expand the time needed for the molding material to cool during or after injection.